1. Field of the Invention
The present invention relates to an ink set for ink-jet recording with which the color bleed is reduced and it is possible to perform vivid color recording, and to an ink-jet recording apparatus.
2. Description of the Related Art
In the ink-jet recording method, ink droplets are formed by means of an ink discharging process including, for example, the electrostatic attraction process, a process in which mechanical vibration or displacement is applied to the ink with a piezoelectric element or the like, and a process in which bubbles are generated by heating the ink to utilize the pressure generated thereby, and all or a part of the ink droplets are adhered to a recording objective such as paper to perform the recording.
Those hitherto used as the ink to be used for the ink-jet recording method as described above include those in which a variety of water-soluble dyes or water-dispersible pigments are dissolved or dispersed in liquid media each comprising water or a combination of water and water-soluble organic solvent.
In order to adequately perform the recording for a long period of time by using the ink for ink-jet recording, for example, it is necessary to satisfy the following conditions. That is, the characteristic values including, for example, the viscosity, the surface tension, the electric conductivity, and the density of the ink for ink-jet recording to be used are appropriate values. The recorded image is excellent, for example, in water resistance and light resistance. In order to avoid any clog-up at the nozzle or the orifice of the recording apparatus, no deposited matter is generated and no physical property value is changed by the influence of heat or the like. A large number of suggestions have been made in order to satisfy the conditions as described above. For example, in order to avoid the clog-up at the nozzle or the orifice, a water-soluble organic solvent is generally added.
In order to obtain good printing qualities, exclusive ink-jet paper is sometimes used. However, in recent years, it is more demanded to perform the recording on the regular paper rather than the recording on the exclusive ink-jet paper, in view of the cost and the consideration of the environment. However, in the case of most of the conventional inks, when the recording is performed on the regular paper, the following problems have arisen. That is, the blurring at the ink edge portion, which is called “feathering”, is apt to occur. Further, the color bleed is apt to occur, which is caused such that the colors are mixed with each other when the different colors are adjacent to one another. As a result, the printing qualities are deteriorated. Especially, the blurring tends to be conspicuous at the ink boundary, for example, when letters or characters are recorded with a black ink having a relatively dark color on the background of a color ink having a relatively bright color such as yellow, magenta, or cyan.
In order to solve the problems as described above, Japanese Patent Application Laid-open No. 6-24006 discloses a method in which a black ink and a color ink are allowed to have different surface tensions to avoid the color bleed. However, in the case of this method, for example, it is necessary that the one dot unit of the black ink is constituted with a plurality of ink droplets due to the difference in surface tension. Further, it is necessary that the black ink and the color ink are subjected to the recording with a certain time difference. Therefore, this method involves a lot of restrictions for the printer mechanism.